Expansion of a virtual GP service where patients are consulted over smartphones risks “destabilising care” for the most complex and vulnerable cases, a heath professor warned.

If rolled out more widely, the NHS GP at Hand service would “cream off” fit young patients from existing practices at the expense of those with the greatest needs, said Martin Rowland, emeritus professor of health services research at the University of Cambridge.

Millions of NHS patients in London and Birmingham can sign up to the service, which offers a GP consultation via a smartphone 24 hours a day.

If a patient needs a face-to-face appointment, they must travel to clinics.

The app offers a symptom check for patients and video GP consultations within hours, but has been accused of “cherry-picking” healthy patients.

More than 50,000 people have enrolled at the service, created by private health provider Babylon.

An independent evaluation by Ipsos MORI found that patients using the service were younger than the average NHS GP patient in London, with just 0.1% of patients being cared for by its “chronic care team”.

Prof Rowland, who was a GP for 35 years, told PA the practice was meeting the needs of a particular group of people “but not addressing the wider needs of the population”.

He said: “It’s essentially taking money away from practices.

“This hasn’t happened to a great degree because clearly GP at Hand has only taken a small number of patients from any one practice, but if you are making the situation where, in a hypothetical example, GP at Hand took away all the patients away from the practice and left the practice just with the chronically ill and elderly, and the funding didn’t reflect that, then essentially those GPs would have even less money to look after those older people.”

Writing in the BMJ, Prof Rowland said a recent independent evaluation had found that some part-time GPs felt the app had allowed them to increase their NHS work.

He continued: “However, the current NHS funding formula does not adjust adequately for the costs of providing a comprehensive primary care service, and the NHS needs urgently to review its arrangements that have allowed a private company to cream off fit young patients from existing NHS practices.

“If the GP at Hand model became widespread, it would risk destabilising care for patients with the greatest needs and those who need regular proactive care.”

The independent review, published in May, found that large numbers of older people with more complex health needs were not enrolling, and that the patient profile “raises questions” about the service’s financial effects on the wider health system.

It said a wider roll-out may require “ongoing health system reform, and the scale of the redesign needed should not be underestimated”.

Richard Vautrey, chairman of the BMA’s General Practitioners Committee, said at the time that the findings raised the “question of whether a wider rollout in an already overstretched NHS would be able to cope with additional demand”.

He added: “Ultimately, the NHS must decide what it wants to prioritise — quick access or continuity and quality of care — because one is likely to come at the price of the other.”

An NHS spokesman said: “The NHS has already changed GP funding arrangements to account for new digital services and are currently consulting on further changes to funding and commissioning rules.

“As set out in the new GP contract, the NHS is committed to supporting GPs to increase the use of digital technology, with every patient in England having access to online and video consultation by 2021 if they choose it, and this practice is just one of the ways of providing that.”